Neither coil lug shows voltage with the game on.

No voltage at either lug of a coil

Cause: The coil may be on the bank-switched side and the L/R relay is not selecting it, the relay is faulty, or the daisy-chained power wire is broken before this coil.

Checks

• Enter diagnostics, which releases the L/R relay, and measure again (not on Time Machine to The Simpsons, where the banks are reversed).
• Still nothing, or a Time Machine to Simpsons game: ground Q29's tab to pull in the relay and measure again.
• A relay fault always affects more than one coil; check its joints on the PPB board.
• Trace the power wire back through the earlier coils on the chain.

Fix

• Repair the broken power wire or the relay solder joints.

Keep hands off coil lugs and the solenoid supply while the game is on; 50 V coil circuits read up to about 80 V unloaded.

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• Low coil voltage from pitted L/R relay contacts
• Only flash lamps work when a game starts (L/R reversed games)
• Use the manual's coil/flasher chart to find driver transistors
• A low resistance coil means checking its driver chain too
• Flash lamp resistors on the PPB drop solenoid voltage for 12 V bulbs
• All L or all R bank coils/flashers dead: PPB relay K1
• L/R relay burnt or intermittent
• A coil or flasher comes on and stays on at power-up

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)